1. Field of the Invention
The present invention relates to apparatus and methods for non-impact printing of halftone or continuous tone information and the like with small pixels (dots).
2. Description of the Prior Art
In published International Patent Application WO 91/10311, the contents of which are incorporated herein by this reference, a method and apparatus for recording grey level pixels is described which includes controlling exposure pulse durations of radiation-emitting recording elements by a non-linear clock. In such method and apparatus, a multibit data signal is compared with a time-changing count from a counter and pulse duration controlled on the basis of the comparison between the data and the count. The time-changing count of the counter is changed by a programmable exposure clock that includes a master clock and a programmed counter that receives a multibit number representing a count or transition time and determines when a pulse is to be output by the counter. A disadvantage with the method and apparatus of the prior art is that if exposure clock edges are required to be one or two master clock cycles apart and the master clock is say a 40 MHz oscillator, very fast processing is required to load successive transition times. Very fast processing can have negative impacts on power requirements and potential electromagnetic emissions and may require more expensive circuit components.
It is therefore an object of the invention to overcome the deficiency of the prior art.